As the concept of managing nature as an ecological system rather than simply a group of dissociated parts makes its way into fisheries, decision-makers are starting to think in fundamentally different ways about the causes of overfishing — and the ways to reverse it.

Overfishing can be seen as simply the result of catching too many fish. But Jim Wilson, a professor of resource economics at the University of Maine, says others believe that the way people fished may also have undermined the structure of a particular fish community.

In the Gulf of Maine, for instance, cod near the shore were fished hard in the 1930s and ’40s until they disappeared, and half a century of no fishing in those areas has not brought the fish back.

Fishermen and scientists now think that those cod may have adapted — either biologically or behaviorally — to spawn in specific areas. When those fish were gone, the genetic or learned information about where to reproduce was gone, too.

Will the most valuable fish species ever return so they can be fished sustainably in the Gulf of Maine?

Andrew Rosenberg, who served as Northeast regional administrator for the National Marine Fisheries Service until mid-July and now is deputy assistant director of NMFS in Washington, D.C., is optimistic that they will. But fish populations here will never look as they did before Europeans began fishing these waters, he says, and the basic philosophy behind current fisheries management holds that they never should.

“The theory of harvesting says you want to manage for a population that’s growing as rapidly as possible so that you can crop off the growth and keep it stable,” Rosenberg explained.

That concept, known as maximum sustainable yield, or MSY, is based on the same idea as thinning a crowded stand of trees: Cut out the older ones, leave just the quick-growing ones, and keep thinning them so that they grow quickly.

At least that’s how it’s supposed to work.

Spencer Apollonio, who headed the Maine Department of Marine Resources for 10 years, is one of the people who says that managing fisheries for maximum sustainable yield is dead wrong. In fact, Apollonio argues that basing the future of fisheries on that theory will unravel the whole system.

By eliminating most of the age diversity in each fish stock, he says, the species becomes more vulnerable to outside forces and responds to those forces in unpredictable ways. Apollonio says that changing fish populations to allow for faster growth of fish changes how they act and respond to outside threats. Those changes will allow fishermen to take a lot of fish, he says, but not to take those quantities over a long period of time.

Bob Steneck, a professor of marine science at UMaine’s Darling Marine Center, agrees with Apollonio that maximum sustainable yield hasn’t worked. For one thing, he and other scientists say that relying exclusively on younger fish is not the most efficient way to replenish their numbers.

Older lobsters, Steneck said, produce 10 to 100 times the number of eggs that smaller lobsters do. Ed Trippel, a Canadian research scientist with the Department of Fisheries and Oceans in St. Andrews, New Brunswick, found that older cod reproduce more successfully than their younger counterparts and so contribute more to their populations.

Steneck says scientists do not have a detailed enough understanding of the way the marine ecosystem functions to make models that can reliably predict responses to a variety of factors. Also, he says, humans taking fish from the sea reverse the natural removal pattern. Nonhuman predators exclusively take the smallest and sickliest prey first. But humans begin by harvesting the biggest and the best, eventually leaving only the youngest animals of reproductive age.

New era of management

But despite Steneck’s and Apollonio’s criticisms of the basic theory of fisheries management, Ellie Dorsey, a senior scientist for the Conservation Law Foundation in Boston, thinks that MSY would be a step forward for the Gulf of Maine.

She said that there may be some fatal flaws with the concept of maximum sustainable yield, but she says New England will have taken a major step if it re-establishes the quantity of fish the scientists say is capable of producing a maximum sustainable yield. “We haven’t seen that biomass for decades, in most cases,” she said.

Dorsey’s organization sued federal fisheries managers after the New England Fishery Management Council in 1988 decided not to reduce ground fish catches despite a recommendation by fisheries scientists to cut the catch by 50 percent.

CLF’s suit led to the development of a new plan for managing New England’s ground fish stocks, known as Amendment 7. The ongoing problems, of which the council’s 1988 decision was a symptom, helped shape key components of the 1996 revisions to the 20-year-old Magnuson Fisheries Conservation and Management Act.

“In some sense what had occured with New England ground fish or New England fisheries in general had been the poster child for why the fisheries law needed substantial strengthening,” said Rosenberg of the National Marine Fisheries Service. “There had been delay after delay of implementing strong management rules … because the industry had intense resistence to any restrictions and they were successful in being able to block those from moving forward.”

The revised law, now known as the Magnuson-Stevens Act of 1996, requires that the regional fisheries councils and NMFS minimize the amount of species caught accidentally when fishermen are fishing for other species; designate essential fish habitat; end overfishing; and rebuild depleted fish stocks.

The law also specifically mandates maximum sustainable yield as the way to prevent overfishing — an inclusion Apollonio believes is a dire mistake.

Managing an ecosystem

Rich Langton, the ecology division director for Maine’s Department of Marine Resources, is part of a national panel advising NMFS about implementing plans to manage the ecosystem rather than just individual species or groups of species within it. He agrees with Apollonio that such plans must take into consideration the dynamics of the marine ecosystem at all levels.

“We need to start understanding those subtleties so that we can hopefully strategically manage our fisheries rather than sort of react to a crisis,” Langton said.

Robert L. Stephenson, a research scientist with the Canadian Department of Fisheries and Oceans in St. Andrews, New Brunswick, says the next challenge is to take the concept of ecosystem management beyond theory and turn it into action.

“It’s fashionable to say we have to manage on a larger scale, at an ecosystem level, but how you do that is up in the air,” he said. “We’re a long way away from understanding everything. But to me that’s irrelevant. We have to manage with respect to the ecosystem in spite of the high level of uncertainty.”

The answer, he says, is to take what is called a precautionary approach to management — another term that is still in the process of being defined.

To Les Watling, a University of Maine Oceanography professor who studies the ecology of the Gulf of Maine’s muddy bottoms, proceeding cautiously means shifting the burden of proof about sustainable fishing from the scientist to the person taking fish from the ocean.

“How do fishermen differ from oil drillers? They are resource extractors. They are taking a resource from the sea, so they should have to demonstrate that their taking of that resource is not doing irreversible damage to the ecosystem.”

Fish populations stand no chance whatsoever, he says, as long as the places where they once hid are open to invasion by newer and more efficient nets. He suggests regulating activities at sea like those on land: by zoning the sea bottom.

“That means that fishermen and everyone else have to accept the idea that you just can’t go anywhere with your gear,” he said.

Sanctuaries and co-management

The concept of marine reserves is not new, although as the concept gains more currency, more voices emerge debating whether the reserves should protect everything in them or just some species, where they should be located and whether they should be permanent.

“Imagine if Baxter were a temporary park,” said Ron Huber, director of the Rockland-based Coastal Waters Project and a proponent of no-fishing reserves. “Every 30 years you could come in and flatten it, and then it would still be a park.”

So little is known about the complex interactions of the Gulf of Maine ecosystem, he says, that the most precautionary approach of all should apply.

“The ecosystem managment modeling is only garbage-in-garbage-out until you have genuine undisturbed marine areas to use as base lines. And if you don’t, you’re just modeling with insufficient data and we know that that takes you nowhere.”

Rosenberg, of NMFS, says there are more fishing closures in this region than anywhere else in the country. But Rosenberg says the zero-extraction reserves Huber champions are simplistic. They also raise a variety of equity issues, he says, since a given closure will disproportionately affect the small fishermen in the nearest ports.

Some industry representatives suggested closing 50 percent of the Gulf of Maine to fishing in an effort to protect habitat. Rosenberg’s staff in Gloucester, Mass., suggested several different closure sites, he says, and at the public hearings people were shocked that the closed areas included popular fishing grounds.

“If you do it and you do it genuinely you’re going to close a fishing ground,” Rosenberg said.

The simple reality, many say, is that fishermen must be a part of the solution in real terms or they will simply find ways around unpalatable rules — and, said Wilson, the UMaine economist, “you’d need the Fourth Army Division up here to police the thing.”

An increasingly popular idea is some form of co-management, which gives stakeholders, including fishermen, a bigger voice in deciding how to fish and how to recover the fish.

Wilson says a good model already exists and has worked well for 200 years — the United States’ form of government, which attempts to balance local, state and national interests. He says that working from the water up, rather than imposing more regulations from Washington may be the only way to restore the fisheries of the Gulf of Maine.

“If we don’t do that over the long haul, we may build up the fish stocks this time, they may come back,” he said. “But we’re going to have episode after episode of just ongoing conflict between managers and fishermen. … It’s going to be Bosnia on the water, periods of peace and then war breaks out.”